Refrigerators have evolved from wooden boxes cooled by a large block of ice to well-insulated appliances cooled by heat pumps. The heat pumps used to remove heat from the interior of the thermally insulated enclosure were first mounted to the top, exterior surface of the cabinet, but were later moved to a chamber beneath the enclosed cabinet.
A conventional refrigerator 10 is shown in FIG. 1. The refrigerator 10 is made up of a rectangular parallelepiped cabinet 12 with a hinged door 14 enclosing the cabinet 12. A recess 16 is formed in the lower rear of the refrigerator 10 and houses a heat pump 18. The heat pump 18 in a typical refrigerator is a conventional Rankine cycle compressor which compresses a refrigerant, the temperature of which increases upon compression. The hot refrigerant is sent through an external heat exchanger 20, and heat is removed by convection currents passing over the heat exchanger 20. The cooled, compressed refrigerant then passes through an orifice into a chamber where it expands and the temperature drops substantially. This cooled, expanded refrigerant then passes through an internal heat exchanger 22. Heat is absorbed from the interior of the refrigerator 10 as the air within the cabinet 12 passes over the cooled heat exchanger 22. The operating temperature of the heat pump 18 is substantially greater than the desired temperature within the refrigerator 10.
The sidewalls of the cabinet 12 and the door 14 are insulated to prevent the flow of heat into the interior of the refrigerator cabinet 12. The heat pump 18 is placed outside the insulated cabinet 12 to keep the heat pump's 18 heat from the cooled cabinet 12, and in the recess 16 to hide the heat pump from view. However, this recess 16 consumes internal volume and increases manufacturing expense. The bends of the refrigerator cabinet, which are necessary to form the recess, may also reduce the insulating properties of the cabinet.
Many improvements have been made to refrigerators, but the heat pump which cools the primary chamber of the cabinet has always been left outside of the insulated cabinet.
U.S. Pat. No. 2,964,912 to Roeder, Jr. discloses thermoelectric devices mounted on the refrigerator doors which, under the Peltier effect, remove heat from chambers formed in the doors and release it to the main refrigerator compartment. These thermoelectric devices make the door chambers cooler, thereby reducing food spoilage in a part of the refrigerator which is usually susceptible to warming because of adjacent thinner insulation and leaks at the door/cabinet seal. The thermoelectric devices act as auxiliary, non-mechanical heat pumps which supplement a primary compressor type heat pump which cools the main compartment.
U.S. Pat. No. 3,821,881 to Harkias discloses similar thermoelectric devices mounted in the door of a refrigerator. The thermoelectric devices cool the interior chamber of the refrigerator and transfer the heat to the exterior of the refrigerator cabinet. The heat dissipation side of the thermoelectric devices is placed outside of the cold chamber of the refrigerator cabinet.
U.S. Pat. No. 1,669,141 to Orr and U.S. Pat. No. 1,736,635 to Steenstrup show prior art refrigerators.
U.S. Pat. No. 5,082,335 to Cur et al. discloses insulating walls for a refrigerator cabinet, as an attempt to increase insulating efficiency.
In U.S. Pat. Nos. 5,127,235 and 5,125,241, Nakanishi et al. disclose noise reduction devices for quieting the operation of a refrigerator. The devices monitor the frequency of refrigerator noise and produce similar noise which is one-half cycle out of phase with the refrigerator generated noise. Destructive interference reduces the noise.
In U.S. Pat. No. 5,335,508, Tippmann shows the use of a pair of cooling systems used simultaneously to increase the efficiency of operation.
In all conventional refrigerators, the heat pump which moves heat energy from the cooled chamber of a refrigerated cabinet to the exterior of the cabinet is mounted outside of the cooled cabinet. In one device, the cooled part of a secondary, Peltier effect heat pump is inside the cooled chamber, but the heat dissipating portion of the secondary heat pump is mounted outside of the cooled chamber of the refrigerator (e.g. Harkias). Another (Roeder, Jr.) uses thermoelectric, Peltier effect heat pumps within the cooled chamber, but these thermoelectric heat pumps merely supplement the primary, mechanical heat pump outside of the cooled chamber.
The placement of the heat pump outside of the cooled cabinet interior has been thought necessary to maintain the highest efficiency refrigerator, since by definition a portion of the heat pump system has an elevated temperature with respect to the cooled chamber from which the heat pump removes heat. Therefore, it is conventionally assumed that keeping the heat pump outside of the cooled chamber results in the greatest cooling efficiency. On the contrary, substantial unexpected benefits are obtained by placing a well-insulated heat pump within the refrigerated cabinet.